Method of manufacturing race for rolling bearing, and apparatus therefore

ABSTRACT

A manufacturing apparatus for the race for a thin cross-section rolling bearing from a heat-treated pipe-shaped material W with a rib section  1  at one end thereof comprises a first spindle  11  having a clamping jig  14  to clamp the rib section  1,  and a chuck  12  to securely hold the clamping jig  14;  a machining unit  23  to process the pipe-shaped material W to form an annular member  10  via turning and/or grinding steps; and a second spindle  28  to retain the annular member, which has been cut off from the rest of the pipe-shaped material W, so that the end face of the annular member is subjected to turning and/or grinding steps, whereby the precision in roundness and uniformity in material thickness of the race is improved.

TECHNICAL FIELD

[0001] The present invention relates to a method for accurately andefficiently manufacturing a heat-treated ring such as a race for therolling bearing, a manufacturing apparatus which is used in the method,and a rolling bearing incorporating the race manufactured by themanufacturing method.

BACKGROUND OF THE INVENTION

[0002] Conventionally, for example, in the manufacture of races for thethin cross-section rolling bearings, the finished part is made throughmany processes from the raw material, the processes involving; turning,heat treatment, surface grinding, external rough grinding, internalrough grinding, external finish grinding, and internal finish grinding(for example, see Japanese Patent Publication No. Tokukai Hei 06-246546,and Japanese Patent Publication No. tokukai Hei 06-246547.

[0003] However, with the races for the thin cross-section rollingbearings, in the conventional process, deformation due to the chuck inthe grinding process and deformation during heat treatment andhardening, are greater than with the races for the general rollingbearings, which becomes a factor for increasing the margin in thegrinding process. Moreover, regarding the heat treated thincross-section race, when it is ground for the internal diameter afterbeing ground for the external diameter, roundness of the externaldiameter becomes worse in precision due to residual stress in theinternal structure. Therefore, roundness must be ensured throughmultiple process repetition. This causes problems which increase themanufacturing cost due to longer processing time, more manufacturingprocesses and the like.

SUMMARY OF THE INVENTION

[0004] An object of the present invention, taking into considerationthese problems of the conventional technology, is to ensure precision inroundness and material thickness uniformity in the race for the thincross-section rolling bearing.

[0005] Another object of the present invention is to address; the pointof forming a heat treated pipe-shaped material into individual shapes ofraces, the point of chucking the pipe-shaped material without affectingthe diameter of the material, and the point of processing multiplenumbers into individual principal race shapes in the chucked condition,in order to solve the problem of significantly suppressing deformationduring grinding and heat treatment which occurs in the conventionalmanufacturing method.

BRIEF DESCRIPTION OF THE DRAWING

[0006]FIG. 1 is a side elevational view with part omitted, showing anembodiment of a first spindle in a manufacturing apparatus of thepresent invention, wherein a pipe-shaped material is illustrated bycross section.

[0007]FIG. 2 is a side elevational view with part omitted, showing anembodiment of a second spindle in a manufacturing apparatus of thepresent invention,

[0008]FIG. 3 is a side elevational view with part omitted, showing anembodiment of a machining unit in a manufacturing apparatus of thepresent invention, where the turning bit and grinding stone are arrangedfor turning step in a direction with reference to the spindles.

[0009]FIG. 4 is a side elevational view with part omitted, showing anembodiment of a machining unit in a manufacturing apparatus of thepresent invention, where the turning bit and grinding stone are arrangedfor grinding step in another direction with reference to the spindles.

[0010]FIG. 5 is a cross-section showing a part of a pipe-shaped materialwith a rib section provided on the internal surface thereof for use inthe present embodiment, where the areas 4 in the drawing denotemanufacture-scheduled races.

[0011]FIG. 6 is a cross-section with part omitted, showing a conditionwhere a clamping jig clamping a rib section of the pipe-shaped materialis chucked by a chuck.

[0012]FIG. 7 is a cross-section with part omitted, showing a conditionof an annular member formed at the free end of the pipe-shaped materialafter turning and grinding and before being cut-off.

[0013]FIG. 8 is an enlarged cross-section of part of FIG. 7.

[0014]FIG. 9 is a cross-section with part omitted, showing a conditionimmediately before the cutting-off step when a second spindle is abuttedto an end face of the annular member for holding the annular member.

[0015]FIG. 10 is an enlarged cross-section of part of FIG. 9 where anannular member is still connected to the rest of the pipe-shapedmaterial.

[0016] FIGS. 11(a) to 11(k) are a diagram showing a series of steps fromturning and grinding of a pipe-shaped material to the cutting-off step,and then turning and grinding of an annular member which has been cutoff from the rest of the pipe-shaped material.

[0017]FIG. 12 is a cross-section showing a clamp configuration in a formwhere a rib section is provided on the external surface of thepipe-shaped material.

[0018]FIG. 13 is a diagram showing a correlation between the materialthickness ratio and the thickness deviation of a race for the thincross-section rolling bearing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] The preferred embodiments of the present invention for solvingthe abovementioned problems are as follows.

[0020] A manufacturing method for a race for the rolling bearingcomprises the steps of: heat treating a pipe-shaped material formed intoa cylindrical shape and provided with a rib section at one end thereof;chucking the one end of the heat treated pipe-shaped material via aclamping jig; forming the other end of the chucked pipe-shaped materialinto an annular member which is approximate to the desired race shape,via turning and/or grinding; holding the annular member on the side ofthe other end; cutting off the annular member from the rest of thepipe-shaped material to provide the annular member with an end face onthe cut side, and subjecting the end face on the cut side of the annularmember to turning and/or grinding.

[0021] A specific process for turning, grinding and cutting in theabovementioned process involves, for example: turning an end face on theafore-mentioned other end, that is on the opposite side to the chuckedend, an external surface and an internal surface of the pipe-shapedmaterial to form an annular member; then grinding the external surface,the end face and the internal surface of the annular member where agroove for raceway is formed in the internal or external surface;cutting off the annular member from the rest of the pipe-shapedmaterial, then turning the end face on the cut side of the annularmember which has been cut-off; and then grinding the end face on the cutside. Moreover, it is possible to omit all the grinding steps, or thegrinding steps except for the grinding of the groove for raceway, fromthe series of steps. Further, it is also possible to omit only thegrinding of the end face.

[0022] In the abovementioned manufacturing method, the pipe-shapedmaterial used can have the rib section provided either on the internaldiameter side or the external diameter side of the pipe-shaped material.The clamping jig used for the abovementioned manufacturing method, isconfigured to clamp the rib section in the axial direction of thecylindrical shape of the pipe-shaped material.

[0023] For the manufacturing apparatus used for manufacturing a racefrom a pipe-shaped material provided with a rib section at an endthereof and formed into a cylindrical shape, the following apparatus isgiven as an example. This apparatus comprises: a first spindle whichholds one end of the heat-treated pipe-shaped material; a machining unitwhich forms the other end of the pipe-shaped material retained by thefirst spindle into an annular member of a desired shape via turningand/or grinding processes and cuts off the annular member from the restof the pipe-shaped material to provide the annular member with an endface on the cut side; and a second spindle which retains the other endof the pipe-shaped material, and which also retains the annular memberwhich has been cut off from the rest of the pipe-shaped material by themachining unit. The end face on the cut side of the annular memberretained by the second spindle is subjected to turning and/or grindingusing the machining unit. The first spindle is provided with a clampingjig which clamps the rib section of the material, and a chuck whichsecurely supports the clamping jig.

[0024] It is also possible to individually arrange a machining unitwhich turns and grinds the pipe-shaped material, and a machining unitwhich turns and grinds the annular member being cut off.

[0025] The rib section can be provided on the internal or externaldiameter side of the pipe-shaped material. The clamping jig isconfigured to clamp the rib section in the axial direction of thecylindrical shape of the pipe-shaped material.

[0026] The second spindle is provided with a support structure forholding the annular member, and is configured to have a retaining faceto mate with the annular member so as to attract and hold the annularmember by magnetic force of the retaining face.

[0027] Moreover, the present invention provides a rolling bearing whichis provided with a race with a material thickness ratio up to 4%manufactured via: heat treating a pipe-shaped material formed into acylindrical shape and provided with a rib section at one end thereof;chucking one end of the heat treated pipe-shaped material via a clampingjig; forming the other end of the chucked pipe-shaped material into anannular member in a predetermined shape via turning and/or grinding;cutting off the annular member from the rest of the pipe-shaped materialto form an end face on the cut side of the annular member; and retainingthe annular member on the side of the other end and turning and/orgrinding the end face formed on the cut side.

[0028] In an example, the race can be manufactured by: turning an endface on the afore-mentioned other end, that is the opposite side to theone end chucked, an external surface and an internal surface of thepipe-shaped material to form an annular member; then grinding theexternal surface, the end face, the internal surface of the annularmember where a groove for a race is formed in the internal or externalsurface; cutting off the annular member from the rest of the pipe-shapedmaterial to form an end face on the cut side of the annular member, thenturning the end face on the cut side of the annular member; and thengrinding the end face.

[0029] In another example, the race can be manufactured by: turning anend face on the afore-mentioned other end, that is the opposite side tothe one end chucked, an external surface and an internal surface of thepipe-shaped material to form an annular member; then cutting off theannular member from the rest of the pipe-shaped material to form an endface on the cut side of the annular member, turning the end face on thecut side of the annular member; and then grinding the end face.

[0030] In another example, the race can be manufactured by: turning anend face on the afore-mentioned other end, that is the opposite side tothe one end chucked, an external surface and an internal surface of thepipe-shaped material to form an annular member; then forming a groovefor a race by grinding in the internal or external surface of theannular member; cutting off the annular member from the rest of thepipe-shaped material to form an end face on the cut side of the annularmember, then turning the end face on the cut side of the annular member;and then grinding the end face.

[0031] In another example, the race can be manufactured by: turning theend face on the afore-mentioned other end, that is the opposite side tothe one end chucked, an external surface and an internal surface of apipe-shaped material to form an annular member; then grinding theexternal surface and the internal surface of the annular member where agroove for a race is formed on the internal or external surface of theannular member; cutting off the annular member from the rest of thepipe-shaped material to form an end face on the cut side of the annularmember, and then turning the end face on the cut side of the annularmember which has been cut off.

[0032] The race can be manufactured using a pipe-shaped materialprovided with a rib section on an internal diameter side thereof.

[0033] The race can be manufactured using a pipe-shaped materialprovided with a rib section on an external diameter side thereof.

[0034] The race can be manufactured via a clamping jig which clamps therib section of the pipe-shaped material in the axial direction of thecylindrical shape thereof.

[0035] A chamfer section is formed through turning on the respectiveraces.

[0036] The aforementioned race for rolling bearing, is directed forexample, to a rolling bearing of the thin cross-section type.

[0037] According to the present invention, after heat treatment of thepipe-shaped material provided with a radially protruding rib section onone end side, it is possible to considerably suppress deformation duringgrinding and heat treatment, which occurs in conventional manufacturingmethods by processing a single pipe-shaped material into a number ofindividual principal race shapes in a condition with the rib sectionchucked via a dedicated clamping jig.

[0038] According to the present invention, the pipe-shaped material isclamped by a standard hydraulic chuck. However, since the pipe-shapedmaterial is previously fixed to a dedicated clamping jig and it is theclamping jig itself which is clamped by the chuck, the pipe-shapedmaterial is finished to a high accuracy from the turning process to thefinal grinding process, without deformation of the material duringchucking.

[0039] Further, in the bearing made by the present invention, after heattreatment, a chamfer section is necessarily subjected to a hard turningprocess, so that the externally produced scale due to the heat treatmentprocess is removed. Furthermore, the chamfer section is processed underthe same chucking reference as for the ground surface, so that the factthat there is no eccentricity can also be detected from the thicknessdeviation measurement. In the case of the outer ring, since there is nothickness deviation of the external diameter and chamfer section, thenwhen the bearing is inserted into the housing, insertion is smoothlyconducted. In other words, this is advantageous for easy execution.

[0040] Hereunder is a description of an embodiment of the presentinvention with reference to the drawings. The present invention shouldnot be interpreted as being limited to just this illustrated embodimentof the present invention, and suitable design modifications are possiblewithin the scope of the present invention.

[0041]FIG. 1 to FIG. 4 show an embodiment of a manufacturing apparatusof the present invention. In the figure, the manufacturing apparatuscomprises a first spindle 11(FIG. 1), a second spindle 28(FIG. 2), amachining unit 23(FIGS. 3 and 4), to process a pipe-shaped material W.

[0042] The first spindle 11 comprises a general hydrealic chuck 12, adedicated clamping jig 14 which is adapted to be grasped by the chuck12, and to clamp the pipe-shaped material W. The second spindle 28comprises a magnet cluck face plate 29 and a retaining section 30. Themachining unit 23 comprises a turning bit 24 and a grinding groove 25which can be changed in angular position as in FIGS. 3 and 4. Inaddition, a cutting-off device (not shown in FIGS. 1 to 4) is providedin the machining unit 23.

[0043] The present invention comprises at least the followingmanufacturing steps (a) to (e), to provide, for example, a race 4 for arolling bearing of the thin cross-section type where the materialthickness ratio in the race 4 manufactured by these steps is 4% or less,and where a chamfer section r is formed by turning on the race 4 (referto FIG. 10 and FIG. 11). The term “material thickness ratio” here iscalculated by the formula of (outer diameter−inner diameter)/2×outerdiameter.

[0044] (a) heat-treating a pipe-shaped material W formed into acylindrical shape and provided with a rib section 1 at one end thereof;

[0045] (b) chucking one end of the heat treated pipe-shaped material Wvia a clamping jig 14 provided on the first spindle 11;

[0046] (c) forming the other end of the chucked pipe-shaped material Wvia turning and/or grinding into a predetermined annular shape, whichbecomes an approximate race shape, to provide an annular member 10having an end face 5 a;

[0047] (d) cutting off the annular member 10 from the rest of thepipe-shaped material W to provide the annular member with an end face 5b on the cut side, and holding the annular member 10 with the secondspindle 28, and

[0048] (e) turning and/or grinding the end face 5 b on the cut side ofthe annular member 10.

[0049] The present embodiment is explained using the race 4 for the ballbearing as an example, however, it is not limited to this, and races ofother bearing forms such as a roller bearings or the like are possiblewithin the scope of the present invention. Furthermore, the presentembodiment is explained using an outer race, however it may of course beapplied to an inner race.

[0050] Hereunder is a description of details of an embodiment ofrespective steps, and an apparatus used in the respective processes.

[0051] “Heat Treatment Step”

[0052] In the present invention, as shown in FIG. 5, a pipe-shapedmaterial W is provided with the radially protruding rib section 1 on theinside surface of one end thereof, and formed (through a preliminaryturning process) into a cylindrical shape of a desired diameter anddesired material thickness. FIG. 5 is a cross-section showing a part ofthe pipe-shaped material W provided with the rib section 1 on the insidesurface thereof for use in the present embodiment, where the areas 4 inthe drawing denote races to be manufactured.

[0053] This configuration of the pipe-shaped material W is simply anexample and is not limiting the present invention.

[0054] That is, in the present invention, the rib section 1 is formedinto an annular shape (continuous circular shape) having a desiredheight in the radial direction and a desired width in the axialdirection of the pipe-shaped material W. However, for example, the ribsection 1 may be intermittently formed around the circumferentialdirection (a rib section formed as protruding segments spaced at desiredintervals around the circumferential direction) of the pipe-shapedmaterial W. Such a pipe-shaped material W is first heat-treated prior tothe machining process such as turning by the machining unit 23.

[0055] For the heat treatment method, a well known heat treatment methodis suitably selected and used. The pipe-shaped material W is made ofbearing steel or the like in the embodiment, but not limited to thissubstance. For example, in the case where the configuration of thesecond spindle 28 detailed later is adopted, this pipe-shaped material Wis desirably able to be magnetically chucked by the magnetic force onthe retaining face of the second spindle 28.

[0056] “Chucking Step for Pipe-Shaped Material”

[0057] After the abovementioned heat-treated pipe-shaped material W isclamped via the dedicated clamping jig 14, the clamping jig 14 isgrasped by the tip chuck 12 of the first spindle 11 as shown in FIG. 1.In the present embodiment, the rib section 1 protruding in the radialdirection of the pipe internal surface W1 of the pipe-shaped material W,is clamped in the axial direction of the pipe-shaped material W by theclamping jig 14.

[0058] As a result, the pipe-shaped material W is indirectly fixed tothe first spindle 11 via the clamping jig 14, and coaxially retained onthe tip of first spindle 11 (refer to FIG. 6).

[0059] Therefore, according to the present invention, since the clampingjig 14 is chucked by the first spindle 11, the thrust due to the chuck12 is exerted on the clamping jig 14, but is not exerted on the ribsection 1. Further, the rib section 1 is clamped by means of theclamping jig 14 in the normal direction to the opposite planes 2 (FIGS.5 and 6) of the rib section 1, that is, in the axial direction of thepipe-shaped material W. Therefore, there is no deformation in the radialdirection of the pipe-shaped material W, so that it is possible toensure precision in roundness and material thickness uniformity aftermachining (refer to comparison data in Table 1).

[0060] Table 1 shows precision in roundness and thickness deviation,comparing the present invention with the conventional technology,wherein the “work” denotes the pipe-shaped material. In Table 1, thechuck pressure of work No.1 is 7 kg/cm², and the chuck pressures ofworks No. 2 and No. 3 are 4 kg/cm². TABLE 1 Comparative Example 1Example 1 NC Lathe Clamped at three- points in Clamped the circum- onthe end ferential faces of the direction rib section Test Apparatus WorkNo. Method of chucking the work 1 2 3 1 2 3 Before- precision on *ex.dia. 12 12 4 1 2 2 Cutting- machine *in. dia. 20 8 4 1 1 1 off (runout)end face 5 17 2 1 1 2 After- roundness *ex. dia. 62 65 93 30 41 51Cutting- *in. dia. 58 66 91 33 38 48 off thickness deviation 13 8 9 2 47

[0061] As previously mentioned, the first spindle 11 is provided withthe general hydraulic chuck 12 at the tip thereof. The dedicatedclamping jig 14 is chucked by the chuck 12, and therefore thepipe-shaped material W that is clamped at one end thereof by theclamping jig 14 is indirectly retained by the hydraulic chuck 12.

[0062] The clamping jig 14 adopts a configuration whereby the ribsection 1 projecting in the radial direction of the pipe-shaped materialW at one end thereof can be clamped in the axial direction (refer toFIG. 6). For example, in the present embodiment, the clamping jig 14comprises a receiving member 15 and a clamping member 19, such that thereceiving member 15 has an external diameter d3 so as to be retained bythe chuck fingers 13 of the first spindle 11, and a retaining section 17of smaller diameter than an internal diameter d1 of the rib section 1protrudingly provided on the tip thereof; and that the clamping member19 is fastened to the receiving member 15 via bolts 18, and has anexternal diameter d4 smaller than the internal diameter d5 of thepipe-shaped material W. By inserting the retaining section 17 of thereceiving member 15 into the inner periphery (internal diameter d1) ofthe rib section 1, and clamping the clamping member 19 inside of thepipe-shaped material W by the bolts 18, the rib section 1 is clamped inthe axial direction between an end face 20 of the clamping member 19 andan end face (stepped section) 16 of the receiving member 15.

[0063] Regarding the abovementioned clamping jig 14, in the presentembodiment, the receiving member 15 is formed in an overall annularshape, and the end face 16 on the outer periphery is formed in anannular shape having a desired height in the radial direction and adesired width in the axial direction of the pipe-shaped material W. Theclamping member 19 is formed an overall annular shape of a desireddiameter and desired width.

[0064] The clamping jig 14 of the present embodiment is simply anexample and the present invention is not limited to this embodiment.That is, for example, the receiving member 15 and the clamping member 19may be intermittently formed around the circumferential direction, andmay be any configuration provided that the receiving member 15 and theclamping member 19 are able to clamp the rib section 1. Therefore, theclamping jig 14 and the rib section 1 may be suitably modified in designwithin the scope of the present invention.

[0065] Moreover, in the present embodiment, the construction is suchthat the rib section 1 of the pipe-shaped material W is clamped by widthadjustment of the interval between the receiving member 15 and theclamping member 19 by bolt tightening via the bolts 18. However, it isof course possible to use another member instead of the bolts 18.Further, the configuration may be such that the receiving member 15 andthe clamping member 19 themselves have respective clampingconfigurations on their respective facing surfaces whereby the ribsection 1 can be clamped by width adjustment of the interval betweenthem. For example, a male screw section and a female screw section maybe directly formed as a unit respectively on the facing surface of thereceiving member 15 and on the facing surface of the clamping member 19,giving a configuration for clamping by screwing these together.

[0066] Furthermore, in the pipe-shaped material W used in the presentinvention, instead of the configuration where the rib section 1protrudes inward in the radial direction from the internal surface ofthe pipe-shaped material W as with the abovementioned embodiment, therib section 1 may protrude outward in the radial direction from theexternal surface. In this case, the clamping jig 14 adopts for example,the configuration exemplified in FIG. 12.

[0067] That is to say, this clamping jig 14 comprises a receiving member15 and a clamping member 19. The receiving member 15 has an externaldiameter d6 such that it can be retained by chuck fingers 13 of thefirst spindle 11, and a retaining section 21 protrudingly provided onits tip and having a smaller diameter than an internal diameter d5 ofthe pipe-shaped material W. The clamping member 19 is fastened to thereceiving member 15 via bolts 18, and has an insertion aperture 22 witha diameter bigger than an external diameter d7 of the pipe-shapedmaterial W and smaller than an external diameter d2 of the rib section1. By inserting the retaining section 21 of the receiving member 15 intothe inner periphery of the rib section 1, and clamping the clampingmember 19 arranged outside of the pipe-shaped material W by the bolts18, the rib section 1 is clamped in the axial direction between the endface 20 of the clamping member 19 and the end face (stepped section) 16of the receiving member 15.

[0068] “Forming and Cutting Steps of the Annular Member”

[0069] As mentioned above, with one end of the pipe-shaped material Wretained by the first spindle 11, the other end or free end 3, that is,opposite to the one end of the pipe-shaped material W which is chucked,is continuously processed from hard turning to grinding by a machiningunit 23 (FIGS. 11(a) to 11(k)) to form an annular member 10, which isillustrated by fine hatching area in the drawings.

[0070] That is to say, firstly, by applying a turning bit 24 of themachining unit 23 to the other end or free end of the pipe-shapedmaterial W, the end face 5 a of the annular member 10 is formed throughturning (FIG. 11(a)). Next, by applying the turning bit 24 to theexternal surface of the pipe-shaped material W, the external surface 6of the annular member 10 is formed (FIG. 11(b)). Then, by applying theturning bit 24 to the internal surface of the pipe-shaped material W,the internal surface 7 of the annular member 10 is formed throughturning (FIG. 11(c)). Moreover, the internal surface 7 is formed with agroove by turning to provide a raceway 8 (FIG. 11(c)). Then, after that,by applying a grinding stone 25 to the external surface 6, the externalsurface 6 is ground (FIG. 11(d)). Then, by applying the grinding stone25 to the end face 5 a, the end face 5 a is ground (FIG. 11(e)). Next,by applying the grinding stone 25 to the internal surface 7, theinternal surface 7 is ground (FIG. 11(f)) and then, by applying agroove-grinding stone 26 instead of the grinding stone 25 to theinternal surface 7, the raceway 8 is formed by grinding (FIG. 11(g)).Through such turning and grinding steps applied to the respective parts,the annular member 10 of a desired material thickness and desired widthfor a race is formed.

[0071] Further, the turning sequence and grinding sequence for therespective parts are not limited to this, and design modifications arepossible within the scope of the present invention.

[0072] For the machining unit 23, for example, a CNC lathe with agrinding stone spindle provided with a general turning bit 24 for theturning section and with a general grinding stone 25 for the grindingsection, is adopted (refer to FIG. 3 and FIG. 4). The turning bit 24 andthe grinding stone 25 are not specifically limited. In the presentembodiment, for the machining means which turns and grinds thepipe-shaped material W and for the machining means which turns andgrinds the annular member 10 after cutting, the same machining unit 23is used. Further, for a cutting-off device 27, a well knownconfiguration is adopted with no specific limitation. The cutting-offdevice 27 can be included in the machining unit 23. The machining unitwhich turns and grinds the pipe-shaped material W may be different fromthe machining unit which turns and grinds the annular member 10 aftercutting.

[0073] As described above, the connecting part 9 of the annular member10, which is formed after turning and grinding of the respective parts,is cut off (FIG. 11(h)) by means of the cutting-off device 27, which isprovided on the rear side of the machining unit 23 in the embodiment.Here, this cutting-off step for the annular member 10, is conducted withthe annular member 10 retained by the second spindle 28 (see FIG. 9 andFIG. 10). Specifically, the second spindle 28 is operated to support theannular member 10 just before the cutting-off step.

[0074] In the present embodiment, a retaining section 30 of the secondspindle 28 (refer to FIG. 9 and FIG. 10) is inserted into the internalperiphery of the annular member 10. Since the second spindle 28 has amagnet chuck faceplate 29, then in a condition where the end face 5 ofthe annular member 10 on the opposite side to the chuck 12 is attractedand retained by the second spindle 28, the connecting part 9 is cut offby the cutting-off device 27 (FIG. 11(h)), and the annular member 10 ofan approximate outer race shape is separated from the rest of thepipe-shaped material W. The annular member 10 is provided with an endface on the cut side (left side in FIG. 11(h)).

[0075]FIG. 7 shows the shape of the annular member 10 processed untilturning, where the shape of the connecting part is effective in order tomaintain the roundness of the annular member 10 during cutting-off (FIG.8 is a enlarged drawing of FIG. 7). At this time, by keeping thematerial thickness and the grinding margin of connecting section to becut to a necessity minimum, it is possible to suppress the residualstress, so that the final product size, roundness and material thicknessuniformity can be ensured by continuous grinding processes for theexternal and internal surfaces.

[0076] “Processing Step of the End Face on the Cut Side”

[0077] The annular member 10 of race shape, which is cut-off andseparated while being retained by the magnet chuck face plate 29 of thesecond spindle 28, is subjected at its end face on the cut side to thefinishing grinding, retained by the second spindle 28, to give thefinished part or race 4 (from FIG. 11(i) to FIG. 11(k)).

[0078] That is to say, in the present embodiment, firstly, with themachining unit 23 which is used for forming the annular member 10, theend face 5 b on the cut-off side is turned by the turning bit 24 (FIG.11(i)). Next, the turned end face 5 b is ground with the grinding stone25 (FIG. 11(j)) to give the finished part or race 4 (FIG. 11(k)).

[0079] Since the second spindle 28 has the magnet chuck face plate 29,and when the retaining section 30 having an external diameter d8 fittedwith the internal diameter of the annular member 10 is inserted into theinternal periphery of the annular member 10, the end face 5 a isattracted and held by the magnet chuck face plate 29 (refer to FIG. 9and FIG. 10). That is to say, the second spindle 28 provides a retainingmeans for the race (annular member) during the cutting-off step, and achucking means for ensuring accuracy of the grinding process for the endface 5 b on the cutting-off side, wherein resistance during thecutting-off step is received by the magnet chuck face plate 29 and theretaining section 30, enabling processing of the end face 5 b with theannular member 10 held by the second spindle 28. Moreover, by previouslyeliminating any run-out of the magnet chuck face plate 29, uniformity inwidth of the end face on the cutting-off side in the product or raceafter grinding can be ensured.

[0080] In the present embodiment, the magnet chuck configuration isused. However, the chuck is not limited to this configurations, therebeing no limitation provided that the configuration is such that theannular member 10 can be retained between the first spindle 11 and thesecond spindle 28, and that the turning and grinding steps by themachining unit 23 after the cutting-off step are possible whileretaining the annular member 10 by the second spindle 28.

[0081] In another embodiment in the present invention, for example, itis also possible to omit, from the abovementioned series of processes,all of the grinding processes, or all of the grinding processes exceptfor the grinding for the raceway forming. Moreover, it is also possibleto omit only the grinding of the end face.

[0082] That is to say, for example, the abovementioned race 4 may bemanufactured by turning the end face on the opposite side to the chuck12, the external surface and the internal surface of the pipe-shapedmaterial W (FIG. 11(a), FIG. 11(b) and FIG. 11(c)) to form the annularmember, then, turning the end face 5 b on the cut-off side of theannular member 10 (FIG. 11(i)) which has been cut off (FIG. 11(h)), andnext, grinding the end face 5 b (FIG. 11(j)).

[0083] Further, it may be manufactured by turning the end face on theopposite side to the chuck 12, the external surface and the internalsurface of the pipe-shaped material W (FIG. 11(a), FIG. 11(b) and FIG.11(c)) to form the annular member 10, next, grinding the internalsurface 7 of the annular member 10 for forming the raceway 8 (FIG.11(g)), after that, turning the end face 5 b on the cut-off side of theannular member 10 (FIG. 11(i)) which has been cut off (FIG. 11(h)), andnext, grinding the end face 5 b (FIG. 11(j)).

[0084] Furthermore, it may be manufactured by turning the end face onthe opposite side to the chuck 12, the external surface and the internalsurface of the pipe-shaped material W (FIG. 11(a), FIG. 11(b) and FIG.11(C)) to form the annular member 10, next, grinding the externalsurface 6, and the internal surface 7 of the annular member 10 with theraceway 8 formed on the internal surface 7 (FIG. 11(d), FIG. 11(f) andFIG. 11(g)), and after that, turning the end face 5 b on the cut-offside of the annular member 10 (FIG. 11(i)) which has been cut off (FIG.11(h)).

[0085] Here FIG. 13 shows a correlation of material thickness ratio andthickness deviation for the race for a thin cross-section rollingbearing manufactured by the present invention and a conventional racefor rolling bearing The term “material thickness ratio” is calculated bythe formula of: (outer diameter−inner diameter)/2×outer diameter. Theterm “thickness deviation” means the ratio of the material thickness ofthe race to the inner diameter of the race. For the present invention,the race is manufactured by the manufacturing method of theabovementioned embodiment, while for the conventional, the race ismanufactured by a grinding method using a shoe type centerless grinder(external surface and internal surface). According to the graph in FIG.13, as the material thickness ratio becomes close to more than 5%, thethickness deviation (μm) of the present invention becomes close to thatof the conventional to some degree. However, when the material thicknessratio is less than 4%, the difference is remarkably apparent. That is tosay, for the conventional, as the material thickness ratio becomes lessthan 4%, the thickness deviates rapidly. However for the presentinvention, even if the material thickness ratio becomes close to 1%,there is not much change, and the degree of thickness deviation isminimal.

[0086] According to the present embodiment, when the annular member 10(individual shape) is formed before the grinding process, by providing aauxiliary groove or connecting portion for cutting-off the annularmember 10 from the rest of the pipe-shaped material W and by minimizingthe cutting-off margin, it becomes possible to keep the deformation inthe annular member after cutting-off to a minimum.

[0087] Moreover, the finishing process for the end face 5 b on thecutting-off side of the annular member 10 is conducted while retained bythe chuck configuration of the second spindle 28, so that the completepart of race can be finished with a single manufacturing unit 23, givinga significant reduction in manufacturing time.

[0088] As to clamping the pipe-shaped material W through the generalhydraulic chuck 12 in the embodiment of the present invention, thepipe-shaped material W itself is fixed by the dedicated clamping jig 14which is in turn clamped by the general hydraulic chuck 12, andtherefore the pipe-shaped material W gets rid of any deformation duringbeing chucked, so that high precision finishing is possible from theturning step to the finishing grinding step.

[0089] In the rolling bearing produced by way of the present invention,the chamfer section r is subjected to hard-turning after heat-treatment,whereby any scale produced through the heat-treatment step is removed.The chamfer section r is processed with the same chuck reference as theground surfaces, there is no eccentricity, which is found throughmeasurement of thickness deviation. By applying the present invention tothe outer race of a rolling bearing, it becomes easy to insert therolling bearing into the housing because the outer race has no deviationin outer diameter and material thickness.

What is claimed is:
 1. A manufacturing method for a race for a rollingbearing comprising the steps of: heat-treating a pipe-shaped materialformed into a cylindrical shape and provided with a rib section at oneend thereof; chucking the one end of said heat-treated pipe-shapedmaterial via a clamping jig; forming the other end of the heat-treatedpipe-shaped material into a predetermined annular shape via turningand/or grinding to provide an annular member; cutting off the annularmember from the rest of the pipe-shaped material to provide the annularmember with an end face on the cut side; retaining the annular member onthe side opposite to the cut side, and processing the end face on thecut side of the annular member via turning and/or grinding.
 2. Amanufacturing method for a race for a rolling bearing according to claim1, wherein the forming step comprises: turning an end face of the otherend opposite to the one end chucked, an external surface and an internalsurface of the pipe-shaped material to form the annular member; thengrinding the external surface, the end face, and the internal surface ofthe annular member with a groove for raceway formed on one of theexternal and internal surface; and the processing step comprises;turning and then grinding the end face on the cut side of the annularmember.
 3. A manufacturing method for a race for a rolling bearingaccording to claim 1, wherein the forming step comprises: turning an endface of the other end opposite to the one end chucked, an externalsurface and an internal surface of the pipe-shaped material to form theannular member; and the processing step comprises; turning and thengrinding the end face on the cut side of the annular member.
 4. Amanufacturing method for a race for a rolling bearing according to claim1, wherein the forming step comprises: turning an end face of the otherend opposite to the one end chucked, an external surface and an internalsurface of the pipe-shaped material to form the annular member, and thenforming a groove for raceway in the internal surface of the annularmember by grinding; and the processing step comprises; turning and thengrinding the end face on the cut side of the annular member.
 5. Amanufacturing method for a race for a rolling bearing according to claim1, wherein the forming step comprises: turning an end face of the otherend opposite to the one end chucked, an external surface and an internalsurface of the pipe-shaped material to form the annular member; thengrinding the external surface, and the internal surface of the annularmember with a groove for raceway formed on one of the internal andexternal surfaces, and the processing step comprises; turning and thengrinding the end face on the cut side of the annular member.
 6. Amanufacturing method for a race for a rolling bearing according to anyone of claim 1 through claim 5, wherein the rib section of thepipe-shaped material is provided on an internal diameter side of thepipe.
 7. A manufacturing method for a race for rolling bearing accordingto any one of claim 1 through claim 5, wherein the rib section of thepipe-shaped material is provided on an external diameter side of thepipe.
 8. A manufacturing method for a race for a rolling bearingaccording to any one of claim 1 through claim 7, wherein the clampingjig clamps the rib section in the axial direction of the cylindricalshape of the pipe-shaped material.
 9. A manufacturing method for a racefor a rolling bearing according to any one of claim 1 through claim 8,whereby a race of the thin cross-section rolling bearing ismanufactured.
 10. A manufacturing apparatus for a race for a rollingbearing comprising: a first spindle which retains one end of apipe-shaped material formed into a cylindrical shape and provided with arib section at the one end thereof; a machining unit which processes theother end of the pipe-shaped material into an annular member of adesired shape via turning and/or grinding processes; and a cutting-offdevice which cuts off the annular member from the rest of thepipe-shaped material; a second spindle which retains the annular memberbefore and after being cut off by the cutting-off device, said machiningunit being used in order that the end on the cut side of the annularmember is subjected to turning and/or grinding processing while theannular member is retained by said second spindle, and the one end ofthe pipe-shaped material being formed with a rib section, and said firstspindle being provided with a clamping jig which clamps the rib sectionof the pipe-shaped material, and a chuck which securely supports theclamping jig.
 11. A manufacturing apparatus for a race for a rollingbearing according to claim 10, wherein the machining unit comprises afirst machining means which turns and grinds the pipe-shaped materialand the annular member formed in the pipe-shaped material and a secondmachining unit which turns and grinds the annular member after being cutoff.
 12. A manufacturing apparatus for a race for a rolling bearingaccording to either one of claim 10 and claim 11, wherein the clampingjig is configured to clamp the rib section in the axial direction of thecylindrical shape.
 13. A manufacturing apparatus for a race for arolling bearing according to claim 12, wherein the clamping jig isprovided with a configuration for clamping a rib section provided on theinternal diameter side of the pipe-shaped material.
 14. A manufacturingapparatus for a race for rolling bearing according to claim 12, whereinthe clamping jig is provided with a configuration for clamping a ribsection provided on the external diameter side of the pipe-shapedmaterial.
 15. A manufacturing apparatus for a race for rolling bearingaccording to any one of claim 10 through claim 14, wherein said secondspindle is provided with a retaining face to mate with the annularmember, and configured so as to attract and hold the annular member bymagnetic force of said retaining face.
 16. A manufacturing apparatus fora race for rolling bearing according to any one of claim 10 throughclaim 15, for manufacturing a race of the thin cross-section rollingbearing.
 17. A rolling bearing having a race which has a materialthickness ratio up to 4%, and is manufactured via: heat-treating apipe-shaped material formed into a cylindrical shape and provided with arib section at one end thereof; chucking the one end of the heat treatedpipe-shaped material via a clamping jig; forming the other end of thechucked pipe-shaped material into a predetermined annular shape viaturning and/or grinding to form an annular member; cutting off theannular member from the rest of the pipe-shaped material to provide theannular member with an end face on the cut side; and retaining saidannular member on the side of the other end, and turning and/or grindingthe end face thereof on the cut side.
 18. A rolling bearing according toclaim 17, wherein said race is provided with a chamfer section byturning.
 19. A rolling bearing according to either one of claim 17 andclaim 18, wherein the rolling bearing is of the thin cross-section type.